ICEngineering Subjects

Tuesday, February 12, 2013

STX RX-8: Ramping Up For 2013

The 2013 Solo season is fast approaching, with the first event of the year being a Match Tour in Wilmington, OH on April 6th. That's a national level event at a new highly anticipated site, so it should be very popular and a potentially very demoralizing way to shake off the cobwebs.

In anticipation for things to get going again, I've been buying/making a lot of stuff so hopefully the car will be even better than it was last year. It's costing me a lot of money, so it had better be worth something!

#1: Dampers

I detailed a little bit of the build-out of my single adjustable Koni Sport dampers in an earlier post. That was pretty much the cheapest way that I could come up with to get a decent set of coilovers on the car, and those shocks have served me very well over the past 5 years. They definitely have some issues, like needing to be removed from the rear of the car to adjust rebound (so I pretty much never do it) and not having enough damping to control wheel hop on launch. They are also the same length as stock, though my car is nearly 2" lower than stock, so usable travel is pretty small, and it turns out that there's a reason why the stock spring is so huge in diameter, because the small-diameter race springs rub the shock bodies over bumps. I've dealt with these things for 3 years, so it's not like it's killing me, but my expectations for results have been raised significantly due to the car's performance last year so I was pretty set on a damper upgrade.

At Nationals, I had poked around the paddock a bit to see what kinds of dampers people were running so I could get an idea of what the fast guys did. I decided that I wanted something double adjustable (rebound and compression) and preferably a monotube so I could run the rears inverted and not have to deal with the springs rubbing. Those two requirements immediately put me up in the Moton/Ohlins territory that was greater than $5000 for a set of dampers.

Instead, I decided to take advantage of the modular construction of my existing dampers and I would have them revalved with higher damping rates and converted to double adjustable or at the very least, have the rear rebound adjustment be made external. This would run me about $1200 and wouldn't fix all of my problems, but it captures 90% of the improvement that I was looking for at about 20% of the cost.

This all changed when at the end of October 2012, I stumbled upon somebody on selling a set of Koni 2812's. These are Koni's top-of-the-line double adjustable aluminum bodied monotubes with some extra-fancy proprietary valving arrangement. They weren't cheap, but they also weren't $5000, so I waffled over it for a while like I always do about big purchases and then bought them.

Old vs New
So that's a big deal. I've done a little bit of stuff with these, and that'll be detailed later, but I'm pretty excited to see how this will affect performance.

#2: Limited Slip Differential

Another gigantic purchase that I had been seriously on the fence about is an upgraded differential. The RX-8 comes with a helical-gear Torsen-style differential which is theoretically great and it works pretty well, but it's totally untunable and I don't think that it's quite right for what I need the car to do. This is a tough decision similar to what I went through with the dampers because I know that the existing solution works, but there are better solutions out there. Unfortunately, it's nearly impossible to quantify the benefit of those better solutions, making the cost/benefit ratio indeterminate.

So...I decided to just bite the bullet and get the best/most expensive diff available for the RX-8; the OS Giken Super Lock LSD.

It took me a while to figure out what was going on inside the OS Giken diff that was not happening in other clutch type diffs like Kaaz and Carbonetic, but when I finally got it, I deemed that it was enough difference to warrant the $500 cost difference. I hope that's true. And I'll never know if it is, so it doesn't matter.

In preparation for this, a good friend Rob and I pulled the car out of winter storage (wherein it is nearly touching the south wall of my garage to make room for the Starlet) and stood it up on stands to begin the brutal dismemberment of the rear end of my car (again) so that we can get the diff out.

The car is unbelievably dusty

Again, there will be more on that later.

#3: Wheels and Tires

I've been running on these cheap but heavy 5Zigen FN01-RC wheels in a 17x9 +43 wheels for a few years now. I got them because they are crazy cheap at around $800 for the set. They also look pretty cool, and I got them at the same time that I got wheels for our white Fit so both cars that we had at the time would match.

Somehow I don't have a picture of the two cars together

However, without exception, anyone who has been nice enough to help me change wheels at an autocross has commented on how obscenely heavy my wheel/tire package is. I've been tempted to buy some lighter wheels for a while but just like with the other upgrades, it was difficult to justify the cost when I already had a workable solution. I got lucky when fellow SE Michigan STX RX-8 driver Brandon decided to sell his Enkei RPF-1's at the end of last season so that he could fit a big brake kit. So now I finally have light wheels. Plus they're gold which is super sweet.

And they've been stored in the car since October

As for tires, there is currently a street tire arms race going on with Dunlop and BFGoodrich having already released their latest and greatest ST-legal tires and there have been talks of an entry from Bridgestone and possibly Kumho. I'm not sure what to do about that yet, so I'm going to wait and see if anybody gets some good testing in before I need to buy tires.

So that's a quick overview of what's happening with the RX-8. I'll get more in depth into some of this stuff when projects start getting completed. I really hope the car will be faster!

Monday, February 11, 2013

Two-Strokes and Electrics

Last kart day of the year, Oct 27 2012!

I'm finally getting around to rebuilding the kart, which has been a spectacular autocross and level-1 fun (fun the whole time) success.  The thing's a blast and a workout - driving it helps slow down the other racing, and the physical requirements helps motivate to get stronger.  True, I haven't gone wheel-to-wheel in the kart yet, so I'm certainly no real karter...

My kart reflects that a little.  I got it used, great deal, great working condition, but it's well-worn.  The frame is Trackmagic, a brand known for it's complete lack of support with some odd-sized parts (need to machine a new lower steering column spacer for next season...), and has mismatched knuckles, some welding on it, etc.  The engine fires on the first couple compressions but the inside of it was otherwise a mystery on purchase. 

So rebuilding the engine was interesting, it was the first time I'd seen what modifications are done to it.  The answer is not many...the ports are smoothed, but stock shape and size, transfers are all stock, compression is stock.

As usual, first step is turning working things into piles of gears
Look at all the 2strokes...
Tray 1 of 2. So many parts for such a simple engine!

What's most interesting is the damage found, there's been some fairly impressive detonation history.

Interesting piston damage

I'm still learning what is normal and what is not for this kind of engine and use.  For instance, in the head, I think the damage below is actually normal-ish for extended use!  Comparing the detonation on the head to the piston, I actually think the piston has been swapped after most of that head damage was done, but the previous owner just kept using the old head... let me know if you think otherwise.

Detonation never looked so evenly distributed
Also detonation around top of cylinder, apparently normal (and some lower in the cylinder?...strange)

I ordered a new piston (fancy Wiseco GP, forged) with rings, and I have a new head...that's it for the cranktrain!  It'll go back together with the old cylinder, and the bottom end is good.  Looking for a stock ignition now to get rid of some ballast, and maybe will increase compression ratio by machining the cylinder in the summer if I'm feeling comfortable.  Only thing keeping the kart engine from reassembly is some transmission small parts still on order...about $100 worth of tiny overpriced washers and bushing which I had damaged the first time I ran the kart...without trans fluid...

I'm slapping it back together because again, the purpose of this thing isn't top-level karting, still just practice and experience.  I'd decided to keep this kart and engine going until 4-strokes were legal (expecting 1-2 more years for autocross) and then go in for some nicer stuff.  I am looking forward to racing a kart with less oil burning and noxious pollution.  It would be nice for my interests in car racing and mountain biking to be less opposed, not to mention becoming less of a giant tool who selfishly contributes to ruining the world by purposely running unbelievably polluting things for fun...

However, now I don't think I'll ever go 4stroke.  I think my next kart will be electric. (And yes, I am concerned about battery manufacturing and disposal, jury is still out)

The 86g soft LiPo battery in this costs $7 and is rated to 30amps at 8.4V!  Battery technology is truly improving

After taking custody of one of Kenneth's older RC cars needing only a once-over and a battery, I have been impressed by the capability now so easily available.  The above battery is essentially rated to 1/3 hp, costs $7, and weighs less than 1/5th of a pound.  It's what's called a lithium-polymer battery, a simplified description of its chemistry.  These have disadvantages in their volatility though.  For application in larger packs, a different chemistry is introduced, LiFe.  I don't really know my history, but I understand A123, the highly-government funded company which has gone bankrupt and just been sold to Chinese investors, is primarily responsible for them.  Among many different characteristics, they are also very resistant to becoming...overactive after being damaged.  You could drive a nail through a LiFe battery pack, and wouldn't expect it to react violently.  A LiPo cell would violently burn and burst, and the chemistry we're used to in cell phones and laptops, lithium-ion, would do similar.  The LiFe cells are what's used for the current generation electric cars.  These are the cells in the Chevy Volt, the Tesla Model S (not the old Elise-based roadster, those were the laptop-type) and also in Zero Motorcycles.  Compared to lithium-ion, LiFe also allow for higher discharge rates, similar to LiPoly.  This is good for Zero Motorcycles, and good for aftermarket, because it allows power to be achieved through amperage instead of voltage.  This is a lot safer to people if anything goes wrong and the electricity tries to short though the user.

Power, Watts, is (volts)x(amps): 1hp is 746W, and that can be achieved with any combination of amps and volts.  It's just that with dry clean hands (which have great electrical resistance) under 100V is generally not enough motivation to hurt a person.  300V on the other hand could be much more...fatal.

So we now have the technology in the battery, and the voltage isn't scary.  The hardware is available.  Additionally, the hardware is available assembled, wired, programmed, and even warrantied!  Motorcycles have donated the 2strokes we use in the karts, and now Zero Motorcycles make their electric drivetrains available to anyone.

This is the 2012 stuff.  2013 has much improved battery packaging

After heavily flirting with the idea, I won't be going electric this year.  Maybe in another 2.  The required components currently cost ~$8800 and the battery to power the 44hp 35lb motor still weighs 85lbs.  I'm excited though.  I am lucky enough to know electric cars can be seriously fast, and now with the market moving as it is, I expect batteries will rapidly improve in both discharge rate and cost.

Lucky me, I know electric can be seriously fast.  And this one is ancient compared to the Volt.

For all the bad press, this one is great to drive.  And I partly love it for the battery progress it's driven.

Monday, February 4, 2013

Miscellaneous Projects: Miata Bits

Interspersed in working on my own projects, I also do little side jobs to help out friends. The last couple were little componentry bits for two different Miatas (Miatae?).

#1: Spherical Bearing A-arm Pivots

The first is Allen's '90 Miata with a turbo BP built for the Super Street Modified (SSM) class in SCCA Solo. I've had the privilege of driving this car a few times in various states of tune, and it's really awesome. It's not quite to the extent of the crazy rules in SSM, but it's getting there.

So my job on this one is to swap the rubber bushings in the front lower control arms out for spherical bearings. This is similar to the job done on the GTI rally car in an earlier post, in that it requires welding in a carrier to hold in a spherical bearing that is then retained by a snapring. Allen actually has some polyurethane bushings for these arms, but stiffer bushings have a lot of potential for bind when the pivot axes aren't perfectly co-linear, which means that every time you change the alignment, you effectively alter the wheel rate. Bushings are also still a bit squishier than sphericals, so the benefit is two-fold: increase joint stiffness and reduce suspension bind. That increase in joint stiffness means less camber loss under lateral load and also a reduction in compliance toe change which are both things designed into the suspension to keep people from getting themselves into trouble. However, this car has been re-purposed exclusively to get into trouble so that is all counter-productive.

Allen requested the use of some fancy seals to keep grit out of the sphericals, so he sent me some detailed project requirements:

This is actually some really awesome MS Paint CAD

 I put it in actual CAD because that's how I think:

Really, this is totally redundant though

As with any other project that I write about, I turned the parts out on the lathe:

Here's the finished bearing carrier:

And then I welded them into the arm and stuffed in the spacers that I made to retain the seal and space the joint up to the same width as the factory bushings and reduce the bearing bore to the factory bolt diameter:

Blast, paint, assemble...and there you have some bind-free, high-stiffness A-arm pivots!

#2: Coolant Expansion Tank

The next Miata is Curt's ride, which also started out as a turbocharged SSM car. Curt exploded his transmission at an autocross last summer though, and that was enough to push him down the tried and true drop-a-giant-V8-in-it path. He's got a really in-depth build going on, and it is impeccably documented on his website here.

Curt first picked up a welder for this project, and he has come an impressively long way in a short time. But he has no way to weld aluminum, so I offered to fabricate a custom coolant tank for him. The coolant expansion tank is exactly what it sounds like; it's a place where the coolant can expand as it gets hot and it's at the top of the system so it also serves as an air bleed. It's basically a box with some fittings and a cap. This one has a sight glass too as an easy way to check coolant level.

Curt made some nice CAD for me and sent me some drawings:

Again, I built my own CAD model because it helps me think, and I changed a couple dimensions to give me some clearance to weld:

There's not much to this except to cut all the pieces out of aluminum and weld them together. I used the lathe to make a huge fitting to thread the sight glass into, but the rest of it was just taking the fittings that Curt sent me and welding them to a box.


Great practice welding aluminum for me. I could use some more, but the part seems sound. And here it is sitting front and center in his engine bay: